Adding soil organic matter primarily improves which property?

• A. Water-Holding Capacity
• B. Soil Texture
• C. Air Quality
• D. Phosphorus Content

Answer: (A)

Water-holding capacity is increased when soil organic matter is added, because organic matter improves soil structure and creates a network of stable aggregates that form many small, well-connected pore spaces. These pores hold onto water between rainfall events, and the organic material itself (humus) has a high surface area and moistening ability, so it can retain more water and make it available to plant roots. This not only boosts how much water the soil can store but also helps keep soil moisture steady, reducing drought stress for plants.

Texture is set by mineral particles (sand, silt, clay); while organic matter can improve aggregation and porosity, it doesn’t fundamentally change the soil’s texture class. Air quality or soil aeration improves with better pore structure, but that’s a secondary benefit to the main effect on moisture storage. Phosphorus content isn’t directly increased by adding organic matter in a way that would be the primary improvement, and P availability depends on other factors like pH and mineral interactions.